49 research outputs found
THE INTEGRATION OF CHINA'S DUAL-TRACK SOCIAL SECURITY SYSTEM AND ITS IMPACT
Master'sMASTER OF SOCIAL SCIENCE
Towards Imperceptible and Robust Adversarial Example Attacks against Neural Networks
Machine learning systems based on deep neural networks, being able to produce
state-of-the-art results on various perception tasks, have gained mainstream
adoption in many applications. However, they are shown to be vulnerable to
adversarial example attack, which generates malicious output by adding slight
perturbations to the input. Previous adversarial example crafting methods,
however, use simple metrics to evaluate the distances between the original
examples and the adversarial ones, which could be easily detected by human
eyes. In addition, these attacks are often not robust due to the inevitable
noises and deviation in the physical world. In this work, we present a new
adversarial example attack crafting method, which takes the human perceptual
system into consideration and maximizes the noise tolerance of the crafted
adversarial example. Experimental results demonstrate the efficacy of the
proposed technique.Comment: Adversarial example attacks, Robust and Imperceptible, Human
perceptual system, Neural Network
Building Universal Foundation Models for Medical Image Analysis with Spatially Adaptive Networks
Recent advancements in foundation models, typically trained with
self-supervised learning on large-scale and diverse datasets, have shown great
potential in medical image analysis. However, due to the significant spatial
heterogeneity of medical imaging data, current models must tailor specific
structures for different datasets, making it challenging to leverage the
abundant unlabeled data. In this work, we propose a universal foundation model
for medical image analysis that processes images with heterogeneous spatial
properties using a unified structure. To accomplish this, we propose spatially
adaptive networks (SPAD-Nets), a family of networks that dynamically adjust the
structures to adapt to the spatial properties of input images, to build such a
universal foundation model. We pre-train a spatial adaptive visual tokenizer
(SPAD-VT) and then a spatial adaptive Vision Transformer (SPAD-ViT) via masked
image modeling (MIM) on 55 public medical image datasets. The pre-training data
comprises over 9 million image slices, representing the largest, most
comprehensive, and most diverse dataset to our knowledge for pre-training
universal foundation models for medical image analysis. The experimental
results on downstream medical image classification and segmentation tasks
demonstrate the superior performance and label efficiency of our model. Our
code is available at https://github.com/function2-llx/PUMIT
Spin excitations in optimally P-doped BaFe2(As0.7P0.3)2superconductor
We use inelastic neutron scattering to study temperature and energy
dependence of spin excitations in optimally P-doped BaFe2(As0.7P0.3)2
superconductor (Tc = 30 K) throughout the Brillouin zone. In the undoped state,
spin waves and paramagnetic spin excitations of BaFe2As2 stem from
antiferromagnetic (AF) ordering wave vector QAF= (1/-1,0) and peaks near zone
boundary at (1/-1,1/-1) around 180 meV. Replacing 30% As by smaller P to induce
superconductivity, low-energy spin excitations of BaFe2(As0.7P0.3)2form a
resonance in the superconducting state and high-energy spin excitations now
peaks around 220 meV near (1/-1,1/-1). These results are consistent with
calculations from a combined density functional theory and dynamical mean field
theory, and suggest that the decreased average pnictogen height in
BaFe2(As0.7P0.3)2 reduces the strength of electron correlations and increases
the effective bandwidth of magnetic excitations.Comment: 7 pages, 5 figures, with supplementar
Dual Active Bridge based Battery Charger for Plug-in Hybrid Electric Vehicle with Charging Current Containing Low Frequency Ripple
High power density is strongly preferable for the on-board battery charger of Plug-in Hybrid Electric Vehicle (PHEV). Wide band gap devices, such as Gallium Nitride HEMTs are being explored to push to higher switching frequency and reduce passive component size. In this case, the bulk DC link capacitor of AC-DC Power Factor Correction (PFC) stage, which is usually necessary to store ripple power of two times the line frequency in a DC current charging system, becomes a major barrier on power density. If low frequency ripple is allowed in the battery, the DC link capacitance can be significantly reduced. This paper focuses on the operation of a battery charging system, which is comprised of one Full Bridge (FB) AC-DC stage and one Dual Active Bridge (DAB) DC-DC stage, with charging current containing low frequency ripple at two times line frequency, designated as sinusoidal charging. DAB operation under sinusoidal charging is investigated. Two types of control schemes are proposed and implemented in an experimental prototype. It is proved that closed loop current control is the better. Full system test including both FB AC-DC stage and DAB DC-DC stage verified the concept of sinusoidal charging, which may lead to potentially very high power density battery charger for PHEV